1. Introduction to
Mycology
03/04/12 Masdiana Padaga 1

2. Fungi versus fungi
“fungus” is used inclusively for a
heterogenous group of organisms that have
traditionally been studied by mycologists
“Fungi” refers to the organisms in the
Kingdom Fungi, the true fungi, also called
the “Eumycota”
03/04/12 Masdiana Padaga 2

3. Introduction to Mycology
Mycology is the study of fungi –
Yeast
Mold
03/04/12 Masdiana Padaga 3

4. Mycology
Yeasts and molds have different structural and
reproductive characteristics
Yeast are unicellular, nucleated rounded fungi while
molds are multicellular, filamentous fungi
Yeast reproduce by a process called budding while
molds produce spores to reproduce
Some yeast are opportunistic pathogens in that they
cause disease in immuno-compromised individuals
Yeast are used in the preparation in the variety of foods
03/04/12 Masdiana Padaga 4

5. Mycology
Fungi serve both beneficial and harmful
roles in our environment
Molds used in the production of cheeses and
also serve an antimicrobial purpose (penicillin).
Molds can be opportunistic infections in
debilitated and immunosuppressed individuals.
03/04/12 Masdiana Padaga 5

6. CHARACTERISTICS OF FUNGI
1. Yeasts
x Unicellular fungi, nonfilamentous, typically oval or
spherical cells. Reproduce by mitosis:
Fission yeasts: Divide evenly to produce two new cells
(Schizosaccharomyces).
Budding yeasts: Divide unevenly by budding (Saccharomyces).
Budding yeasts can form pseudohypha, a short chain of undetached
cells.
Candida albicans invade tissues through pseudohyphae.
x Yeasts are facultative anaerobes, which allows them to grow
in a variety of environments.
When oxygen is available, they carry out aerobic respiration.
When oxygen is not available, they ferment carbohydrates to produce
ethanol and carbon dioxide.
03/04/12 Masdiana Padaga 6

7. CHARACTERISTICS OF FUNGI (Continued)
2. Molds and Fleshy Fungi
x Multicellular, filamentous fungi.
x Identified by physical appearance, colony characteristics,
and reproductive spores.
Thallus: Body of a mold or fleshy fungus. Consists of many hyphae.
Hyphae (Sing: Hypha): Long filaments of cells joined together.
x Septate hyphae: Cells are divided by cross-walls (septa).
x Coenocytic (Aseptate) hyphae: Long, continuous cells that are
not divided by septa.
Hyphae grow by elongating at the tips.
Each part of a hypha is capable of growth.
x Vegetative Hypha: Portion that obtains nutrients.
x Reproductive or Aerial Hypha: Portion connected with
reproduction.
Mycelium: Large, visible, filamentous mass made up of many
hyphae.
03/04/12 Masdiana Padaga 7

8. CHARACTERISTICS OF FUNGI (Continued)
Dimorphic Fungi
x Can exist as both multicellular fungi (molds) and yeasts.
x Many pathogenic species.
Mold form produces aerial and vegetative hyphae.
Yeast form reproduces by budding.
x Dimorphism in pathogenic fungi typically depends on
temperature:
At 37oC: Yeast form.
At 25oC: Mold form.
x Dimorphism in nonpathogenic fungi may depend on
other factors: Carbon dioxide concentration.
03/04/12 Masdiana Padaga 8

9. 03/04/12 Masdiana Padaga 9

10. Hyphae (singular, hypha)
Cylindrical, branching filaments composed
of a tubular cell wall filled with cytoplasm
and organelles
Most fungal hyphae are 2-10 µm diameter
03/04/12 Masdiana Padaga 10

11. Septa
Septa—regular cross-walls formed in hyphae.
Hyphae with septa are septate, those lacking septa
except to delimit reproductive structures and aging
hyphae are called aseptate or coenocytic.
primary septa are formed as a process of hyphal
extension and generally have a septal pore, which
allows for cytoplasmic and organelle movement.
Secondary or adventitious septa are imperforate,
formed to wall off ageing parts of the mycelium.
03/04/12 Masdiana Padaga 11

12. Characteristics of Fungal Hyphae:
Septate versus Coenocytic
03/04/12 Masdiana Padaga 12

13. Mycelium: Large, Visible Mass of Hyphae
03/04/12 Masdiana Padaga 13

14. Fungal cell Structure
03/04/12 Masdiana Padaga 14

15. Fungal cell wall composition
Structural components:
chitin microfibrils [ß(1-4)-linked polymer of
N-acetylglucosamine]
chitosan in Zygomycota [ß(1-4)-linked
polymer of glucosamine]
ß-linked glucans
Gel-like components:
Mannoproteins (form matrix throughout
wall)
03/04/12 Masdiana Padaga 15

16. Other cell wall components
Antigenic glycoproteins, agglutinans,
adhesions—on cell wall surface
Melanins—dark brown to black
pigments (confer resistance to enzyme lysis,
confer mechanical strength and protect cells from
UV light, solar radiation and desiccation)
Plasma membrane—semi-permeable
03/04/12 Masdiana Padaga 16

17. 03/04/12 Masdiana Padaga 17

18. Fungal nuclei
1--3 µm diam
3--40 chromosomes
Up to 13--40 Mb (million base pairs) DNA
coding for 6,000 to 13,000 genes
Intranuclear division--nuclear envelope remains
intact during mitosis (unlike plants and
animals)
03/04/12 Masdiana Padaga 18

19. Fungal nuclei
Usually haploid
Nuclear membrane persists during division
Nuclear associated organelles (NAOs):
Associated with the nuclear envelope; function as
microtubule-organizing centers during mitosis and
meiosis
• Spindle pole bodies
 In fungi that lack a flagellated stage in lifecycle
• Centrioles
 In fungi and other organisms possessing flagellated stage in
lifecycle
03/04/12 Masdiana Padaga 19

20. Other organelles
Mitochondria—flattened or plate-like
mitochondrial cristae in Fungi (similar to
animals)
Golgi bodies—consist of a single, tubular
cisternal element (stacked, plate-like cisternae
in animals and plants)
Other types:
ribosomes, endoplasmic reticulum, vacuoles, lipid
bodies, glycogen storage particles, microbodies,
microtubules, vesicles
03/04/12 Masdiana Padaga 20

21. Storage Compounds
Glycogen, lipids and trehalose in fungi and
animals
Starch in plants
03/04/12 Masdiana Padaga 21

22. LIFE CYCLE OF FUNGI
Filamentous fungi can reproduce asexually by
fragmentation of their hyphae.
Fungal spores are formed from aerial hyphae and are
used for both sexual and asexual reproduction.
1. Asexual spores: Formed by the aerial hyphae of one organism.
New organisms are identical to parent.
x Conidiospore: Unicellular or multicellular spore that is not
enclosed in a sac.
x Chlamydospore: Thick-walled spore formed within a hyphal
segment.
x Sporangiospore: Asexual spore formed within a sac
(sporangium).
2. Sexual spores: Formed by the fusion of nuclei from two opposite
mating strains of the same species. New organisms are different
from both parents. Masdiana Padaga
03/04/12 22

23. Arthrospores are formed by the fragmentation
of septate hyphae
03/04/12 Masdiana Padaga 23

24. Chlamydospores are thick walled spores
formed within a hyphae
03/04/12 Masdiana Padaga 24

25. Sporangiospores are formed within a sac
(sporangium) at the end of an aerial hyphae called
a sporangiophore
03/04/12 Masdiana Padaga 25

26. Sporangiospores
03/04/12 Masdiana Padaga 26

27. Conidiospores are produced in a chain at the end of a
conidiophore. Unicellular conidiospores are called
microconidia
03/04/12 Masdiana Padaga 27

28. Blastospores consist of a bud coming off the
parental cell
03/04/12 Masdiana Padaga 28

29. NUTRITIONAL ADAPTATIONS OF FUNGI
Fungi absorb their food, rather than ingesting it.
x Fungi grow better at a pH of 5, which is too acidic for most
bacteria.
x Almost all molds are aerobic. Most yeasts are facultative
anaerobes.
x Fungi are more resistant to high osmotic pressure than
bacteria.
x Fungi can grow on substances with very low moisture.
x Fungi require less nitrogen than bacteria to grow.
x Fungi can break down complex carbohydrates (wood,
paper), that most bacteria cannot.
03/04/12 Masdiana Padaga 29

30. Fungi are classified based on the
type of sexual spore that they
form
03/04/12 Masdiana Padaga 30

31. Zygomycota
 Have non-septate Zygospores
hyphea
 Have asexual
sporangiospores
 Form sexual
zygospores.
 They are large
spores enclosed in a
thick wall and
formed from the
fusion of two cells
03/04/12 Masdiana Padaga 31

32. Ascomycota
 Have septate Ascospores inside an
hyphae
ascus
 Have asexual
conidiospores
 Have sexual
ascospores.
Ascospores result
from the fusion of
nuclei of two cells.
They are produced
in a sac-like
structure called an
ascus.
03/04/12 Masdiana Padaga 32

33.  Basidiomycota
Have septate hyphae, asexual conidiospores
Have sexual basidiospores. Basidiospores are formed
externally on a base pedestal called a basidium
Basidiospores
03/04/12 Masdiana Padaga 33

34. How do we identify molds in the lab?
 Based on type of hyphae (septate versus non-septate)
 Based on color of mycelium
 Based on reproductive structures
 Molds may form either sexual or asexual spores
 Sexual spores are formed from the fusion of
nuclei from two opposite mating strains of the
same species. They are only formed under
special conditions, but they are used to classify
fungi (more on this later)
 Asexual spores, which are most commonly used
in identification, are formed by the aerial
mycelium of a single organism by mitosis and
cell division
03/04/12 Masdiana Padaga 34

35. ECONOMIC IMPORTANCE OF FUNGI
25-50% of harvested fruits and vegetables are damaged by
fungi.
Fungal infections of plants are commonly called rots, rusts,
blights, wilts, and smuts.
Phytophthora infestans: Caused great potato famine in mid-1800s.
Over 1 million people died from starvation in Ireland. Many
immigrated to the U.S.
x Beneficial fungi:
Candida oleophila: Prevents fungal growth on harvested fruits.
Saccharomyces cerevisiae: Used to make bread and wine.
Genetically engineered yeast strains are used to make proteins
(Hepatitis B vaccine).
Taxomyces: Produces anticancer drug taxol.
Trichoderma: Produces cellulase. Used to make fruit juice.
03/04/12 Masdiana Padaga 35